That usually means that the server doesn't send the file with the correct required MIME (content) type.
In this case the file is send as text/xml instead of application/rss+xml or application/xhtml+xml

A workaround is to use a data URI to get an enabled RSS feed icon on the Navigation Toolbar.
If you do not have the feed icon then open the Customize window and drag the feed icon from the toolbar palette on the Navigation Toolbar.

• https://support.mozilla.org/kb/Back+and+forward+or+other+toolbar+items+are+missing

data:text/html,<link rel="alternate" type="application/rss+xml" title="Add Feed" href="http://www.sermoncentral.com/contributor-rss.asp?ContributorID=12458" /><b>Click the <u>RSS button</u> on the navigation toolbar</b>

Thanks, I assume when you say the feed icon, you mean the subscribe icon. I did not see an icon that specifically said feed icon.. I tried this and still had the same results. Did I do this right.?

Yes, that icon gives a tooltip of Subscribe to this page.

Does that "Subscribe to this page" button get enabled if you paste the data text in the location bar and click the Go button or press enter?

the button appeared off to the left side of address bar, but is grayed out. I don't think it is enabled. Also, I did not get a tooltip to subscribe to this page.

Did you open a new blank tab?

Do you see the "Click the RSS button" text on the navigation toolbar on that page?

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.org/kb/Safe+Mode

I tried it in a new tab with the same results. I am set on the default theme. I also tried starting in safe mode and had the same results.I also get high memory usage error messages from time to time, I've cleared my cache as well. The subscribe to this page icon stays grayed out on this page. I've also tried several addons for rss reading. the only difference I got was on one of them multiple blank tabs were opening up and I had to shut firefox down. Thanks for all of your help.